Dual stage flow back recovery system

ABSTRACT

A flow back recovery system for wells includes a plurality of pressure vessels with baffles and outlets for separating the various components of the flow back fluid. A diffuser is positioned between the well head and the first pressure vessel. The diffuser includes an interior diffuser pipe having a plurality of baffles and outlets. The diffuser pipe may be easily replaced in the field should it wear out due to the abrasive nature of the flow back fluid.

BACKGROUND OF INVENTION

1. Field of the Invention

This invention relates to the handling of flow back materials which occurs during the cleaning or preparation of oil or gas wells for long term production. The flow back material may include a mixture of water, gas, oil, sand, solid rocks or other solids, completion fluid and drilling mud for example. Various components such as filters, sand separators, chokes, liquid gas separators and tanks along with necessary valves, storage tanks and piping are currently used to process the flow back.

2. Description of Related Art

Currently the materials that are recovered during these flow back operations are considered to have little or no commercial value. In most cases the oil, gas, water and sand are all recovered into a common tank wherein the gas is allowed to vaporize to the atmosphere and the sand settles to the bottom of the tank with the oil and water being left to be disposed of or to be manually skimmed and separated during removal. During normal production operations of the well multiple units are used to separate the material from one another. These production separators however are not designed to handle a large amount of contaminates and can become damaged or plugged during this phase of the operation. Therefore the well must be cleaned up and these contaminates removed from the flow prior to the well being placed on long term production. To accomplish this, temporary equipment and facilities that can handle and separate these materials from the commercial commodities are set up. In the past these systems lacked the ability to reclaim or recover the oil and gas mixed with these materials during the flow back. However higher commodity prices and environmental concerns have pushed the oil and gas industry to recover these at much earlier stages during this production. This recovery helps to reduce carbon emissions while selling items that would otherwise be lost to the atmosphere during this stage. As the complexity of this separation process has increased so has the time and cost associated with the transport and set up of the temporary facilities. Before these facilities can be placed into operation the integrity as well as the functional operation of the equipment must be tested and certified as to their operating capabilities. On high pressure operations these rig up or set up operations can be complicated because the connections must be flanged and bolted together. In addition the higher pressure operations require connections and equipment that is much larger and heavier than standard operations to support the extreme pressure. This set up operation may take days to accomplish with each piece being transported to the well location on separate trucks because of their enormous size and weight. Once on location crews of men work with cranes and winch trucks to off load this equipment and precisely set the equipment the proper distance from one another so they may be connected together and pressure tested. Once all of the equipment has been brought in and assembled a truck screws anchors into the ground and each is load tested, then the piping that connects all of the individual pieces are tied to the anchors. This is done so that in the event that connection or pressure lines were to rupture during the operation the restraints would help to contain the release of pressure and energy. In addition spill containment must be put down to prevent oil and other contaminates from soaking into the ground. This entire operation may take several days to accomplish and many accidents, strains and injuries occur during this process. Therefore there is a need to design a system that can eliminate the complexity and reduce the manual labor while improving safety exists.

BRIEF SUMMARY OF THE INVENTION

This invention allows for the on-site treatment of flow back materials through the use of a dual stage process. Additionally a unique diffuser is utilized to reduce the velocity in the high pressure flow back stream as it leaves the well head. A novel combination of separators and storage and containment vessels is utilized to separate the flow back material and the separated products may be further utilized or recycled.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic view of an embodiment of the invention.

FIG. 2 is an end view of an embodiment of a diffuser according to the invention.

FIG. 3 is a cross-sectional view of the diffuser according to an embodiment of the invention along line 3-3 of FIG. 2.

FIG. 4 is a perspective view of the center pipe 64 of the diffuser shown in FIG. 3.

FIG. 5 is a cross-sectional view of the center pipe of the diffuser shown in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, flow back material flows through a well conduit 10 which is connected to a well head in a known manner. The fluid which may contain solids, such as sand, water, oil, other liquids, and gas first passes through one or more diffusers 11 and from there impinges on an inclined baffle 16 suspended from the top of a first pressure vessel 12. The diffuser lowers the velocity of the fluid before it enters pressure vessel 12. The details of an improved diffuser according to one aspect of the invention will be discussed below. As the fluid strikes deflector 16, it will begin to separate into its various components. Solid particles will be deflected downwardly as will fluids. Gas will begin to separate out in the upper section of pressure vessel 12. Two downwardly extending perforated baffles 17 and 18 also aid in separating the gas from the liquid and solid components. A baffle 19 is located in the lower portion of pressure vessel 12.

A number of manual dump valves 20, 21, and 22 for example are located in the bottom portion of pressure vessel 12 and are connected by conduits 24 and 25 to a conduit 23 which leads to an open top sand tank 27 which may be located in close proximity to the flow back system. Thus sand and other particulate material falling to the bottom of pressure vessel 12 may be directed to the tank 27 via the dump valves and conduits shown in FIG. 1. The pressure vessel is also equipped with one or more pressure relief valves 14, 15. The above described apparatus constitutes what may be called the first separation stage.

As shown in FIG. 1, the apparatus of an embodiment of the invention also includes a second pressure vessel 32. Gas from the upper portion of pressure vessel 12 is directed into pressure vessel 32 via conduit 31 and liquid with any remaining solids is directed into pressure vessel 32 via conduit 30. Suitable flanged connectors 81 are provided for the conduits. A baffle 55 is positioned in the lower portion of pressure vessel 32 and acts to separate the water from the oil as the oil floats to the top and is discharged over the top of baffle 55. One or more mechanical dump valves 40, 41 are located in the bottom portion of pressure vessel 32 and are connected by conduits 45 and 46 to conduit 50 which is connected to a closed top tank 51 for storing water and any other liquid chemicals that may have been dissolved or mixed in water. Tank 51 may include a flapper valve 52 and vent 53. Tank 51 may also be a closed pressure tank with one or more pressure relief valves. Pressure vessel 32 also has manual dump valves 42, 43, 44 located in its bottom so that any additional sand or particulate matter may be directed via conduits 47, 48, 54, 49, and 23 to the open top sank tank 27. Oil that collects in lower portion 57 of the pressure vessel 32 can be bled off via mechanical dump valves 62 and conduit 61 to an oil storage tank or production equipment.

Pressure vessel 32 may include one or more pressure relief valves 34, 35 and a gas conduit 36 connected to an upper portion of the vessel. Conduit 36 may lead to a sales conduit 37 or may be directed to a flare via conduits 38, 39. Tank 51 may also have an outlet to a conduit 59 which is connected to flare conduit 39. Pressure vessel 51 may also include one or more pressure relief valves 84, 85.

From the above description it can be seen that flow back fluid from a well treating process flows into diffuser 11 via conduit 10 which initially reduces the velocity of the fluid. Fluid then enters first pressure vessel 12 and begins to separate into its various components.

Gas will begin to form in the top portion while liquid and solids settle to the bottom. Some solids such as sand may initially be removed through manual dump valve 20, 21, and 22. Pressure vessel 12 is connected to a second pressure vessel 32 via gas conduit 31 and fluid conduit 30. Water and oil separate out due to weir baffle 55 in vessel 32. Gas exits pressure vessel 32 at 36. Sand and particulate material can be further separated through manual dump valves 42-44 to sand tank 27.

Water and other chemicals dissolved in the water are withdrawn from the pressure vessel 32 through mechanical dumps valves 40, 41 to tank 51. Oil can be removed from area 57 of pressure vessel 32 via a mechanical dump valve 62 to a holding tank or production equipment.

According to another aspect of the invention, a major portion of the system shown in FIG. 1 can be assembled on a trailer so that it can easily be transported to a well site.

Specifically, diffuser 11, pressure vessels 12 and 32, and tank 51 along with the associated valves, conduits and connectors can all be preassembled on a trailer and tested and certified in advance in the manner described in pending U.S. patent application Ser. No. 12/953,197 filed Nov. 23, 2010, the entire contents of which is hereby incorporated herein by reference thereto.

A novel diffuser in accordance with another aspect of the invention will now be described with reference to FIGS. 2 and 3.

The diffuser 11 includes an outer housing 61 which may be cylindrical and an inner sleeve 62 positioned within and in contact with housing 61. A first connection member 76 with bores 71 is secured to the housing 61 for attaching the diffuser to the inlet of a pressure vessel 12 as shown in FIG. 1. The first connection member 76 includes an opening 73 for the flow back fluid. A second connection member 63 closes the upstream end of housing 61 and sleeve 62 and includes an opening 81 through which diffuser pipe 64 extends.

The details of the diffuser pipe are shown in FIGS. 4 and 5. Diffuser pipe 64 includes a first end 65 for connection to the well conduit 10 shown in FIG. 1. The pipe includes a plurality of upper baffles 68 and lower baffles 70. The baffles are formed by first cutting the pipe perpendicular to its axis to a suitable depth not greater than half its circumference as shown at 67. A rectangular side portion of the pipe is cut out on each side of the pipe as shown at 69. The remaining portions 68, 70 of the pipe can then be bent inwardly about location 72 to form the inwardly projecting baffles. This also forms a plurality of outlets 74 in the wall of the pipe.

Pipe 64 is closed at end portion 66. The pipe can be secured within the housing by suitable supports if desired.

As flow back fluid enters the diffuser through inlet 65, a portion of the fluid is deflected outwardly by the baffles while a portion of the fluid continues to flow within the pipe 65 until it impinges a subsequent baffle. This process continues until all the fluid exits the pipe into the chamber 82 formed between the sleeve 62 and the pipe 64. The velocity of the fluid from the well is thus reduced as it now enters pressure vessel 12.

By virtue of this design, should either the central pipe 64 or sleeve 62 wear out due to the abrasive nature of the flow back fluid, these parts may be easily replaced on site thus saving time and money.

Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims. 

I claim:
 1. A dual stage flow back recovery system comprising: a first pressure vessel having a diffuser at a fluid inlet; a first baffle extending from a lower wall of the pressure vessel; one or more dump valves in the lower wall of the pressure vessel for removing solid material from the pressure vessel; a second pressure vessel having a second baffle extending from a lower wall of the second pressure vessel, the baffle serving to separate a water chamber from an oil chamber; a conduit extending between the first and second pressure vessels at a lower portion thereof for conveying liquids from the first pressure vessel to the second pressure vessel; a second conduit for gas extending between the first and second pressure vessels at an upper portion thereof for conveying gas from the first pressure vessel to the second pressure vessel; a gas outlet conduit in the upper portion of the second pressure vessel for directing gas either to a sales gas line or a flare gas line; one or more dump valves in the bottom of the second pressure vessel for discharging solid material from the second pressure vessel; one or more mechanical dump valves in the bottom of the water chamber for dumping liquid water to a frac tank; a mechanical dump valve in the oil chamber for directing oil to a remote location; and a closed top tank for storing liquid separated out in the second pressure vessel.
 2. The system of claim 1 wherein the components of the system are mounted on a trailer and are pre-assembled and tested for compliance with regulatory requirements.
 3. The system of claim 1 wherein the closed top tank includes a vent and a flapper valve.
 4. The system of claim 1 wherein the first and second pressure vessels and the closed top tank include pressure relief valves.
 5. The system of claim 1 wherein the first pressure vessel includes an inclined baffle positioned to intercept the fluid as it flows into the pressure vessel from the diffuser.
 6. The system of claim 5 further including one or more apertured baffle plates extending from a top portion of the first pressure vessel.
 7. A diffuser for a flow back recovery system comprising: a housing having a fluid outlet at one end and a closed second end with an opening for a diffuser pipe; a diffuser pipe positioned within the housing and including a plurality of inwardly extending baffles; and a plurality of outlets in the diffuser pipe;
 8. The diffuser as claimed in claim 7 wherein the baffles are portions of the diffuser pipe formed by cutting through the pipe and bending the portions into the pipe.
 9. The diffuser as claimed in claim 8 wherein the outlets are formed by bending the baffles inwardly.
 10. The diffuser as claimed in claim 7 further including a sleeve positioned within the housing and in contact therewith.
 11. The diffuser as claimed in claim 7 wherein the housing and the sleeve are cylindrical in shape.
 12. The diffuser as claimed in claim 7 wherein the diffuser pipe is cylindrical in shape. 